I have it too. It's decent. I don't use it much, and I knew I wouldn't as it is a specialty lens. That's why I got this cheap one and not the twice as expensive 10/2.8 fish from Sigma for example. I could justify the purchase of the fairly cheap Samyang pretty easily.
The main thing for me with the Samyang fish is that it's a fun lens! If crazy perspectives and warped images are your thing, then go ahead!

I got it but I dont use it much. I think its a really good and fun lens.

The only thing is that I cant really use it on my 1D Mark IV, it mounts onto it but the result of it is an awkward looking frame around it.

Works great on the 40D though.

_________________http://www.AnderssonPhoto.com Equipment: A blend of Canon, Nikon, Yashica, Leica, Voigtlander, Samyang and Sigma. All of which you can see on my website!Wishlist: Leica M 240, Summilux 50 ASPH, Summilux 24 ASPH

It is intended for APS-C sensor bodies so you can't complain if it doesn't cover bigger sensors. However, I do know of full frame users who use the lens with the built in hood cut off. You still don't get a full frame but it will fill the vertical better.